Effect of CTAB on Colloidal Suspensions of Sepiolite — A Study by Light Scattering, Electric Birefringence, Laser Line Broadening and Electrophoretic Light Scattering
A combination of laser line broadening and electro-optic techniques has been used to investigate the stability of suspensions of the rigid needle-shaped clay sepiolite. In distilled water, sepiolite is negatively charged. Addition of the surfactant CTAB was used to take the clay through its iso-electric point. The minimum stability of the suspension occur-red at the surfactant concentration at which (a) the anisotropy (△α) of the electrical polarisability (α), obtained from electric birefringence data, showed a minimum value, and (b) the electrophoretic mobility, obtained from laser line broadening in electric fields, was zero. The minimum in △α was attributed to the isolation of the bulk polarisation contribution from the otherwise predominant interfacial polarisation contribution.
KeywordsSurfactant Concentration Cetyl Trimethyl Ammonium Bromide Ionic Medium Clay Concentration Translational Diffusion Coefficient
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